Wrote this today and posted it to facebook/twitter. I love taking transit to work, lets me write random ****.
Alright, so I'll flesh out my thoughts with respect to my last status a bit more.
The reason I'm in favour of mii special legality in customs-off is because if we want to decide that an option available under "2/3 stock, 6/8 minutes, no handicap, items off, customs off" is either a) damaging to the meta or b) a significant hindrance to tournament logistics, then we should have thoroughly tested it to prove it.
That's how we developed our stagelists, that's how we developed our stock counts. That's how we developed other "surgical" rules like the ledge grab limit in Brawl, or the starter-only counterpick rule imposed on MK at some Brawl tournaments in southern Ontario. That's how we decided after 14 years to finally ban Hyrule Castle in 64. That's how we decided to ban wireless controllers at majors. That's how we developed Smash as a meta.
Opponents of mii specials, by and large, DO NOT want to do that. They are asking for a blanket ban or arbitrary nerf based on almost no data and bad arguments.
The most popular arguments against mii specials are as follows:
#1: "Nobody else gets to use customs. It's not fair to them."
This is easily the most popular argument against mii specials, and unfortunately its popularity heavily overshadows the fact that it's a horrible argument. What does "not fair" in the context of smash bros even mean? There has been no game in this series' history that did not feature characters having options that other characters don't have. MK vs Ganondorf in Brawl is unfair, but we didn't ban MK for longer than 6 months. Taking Link to Dream Land as Kirby in 64 is unfair, but there's no rule against it. Ice Climbers being two characters in a 1v1 is also an option that nobody else has, and yet nobody except Xanadu Brawl has opted to ban them (in fact the wobbling ban was largely reversed when we all realized it was stupid as a surgical rule - if only history would repeat itself!) Ryu has more attacks at his disposal than any other character in Smash 4, Shulk can literally modify his own properties mid-match, and these are fine despite being unique. In Brawl/Melee, Zelda/Sheik, Samus/ZSS, and Pokemon Trainer all get to literally transform mid-match into characters with entirely new movesets, and nobody batted an eyelash at that. Why are characters with 4 customizable moves that they're locked into per game suddenly a bigger problem that we need to ban because "nobody else can do it"?
And isn't it bizarre how the same people will turn around and say "DLC characters have no customs, so customs tournaments are unfair" is a bad argument? Telling. In fact, the existence of the customs-on meta has been the biggest red herring of all time (sorry Palutena users). Saying "wait, but customs are off, Miis still have them, that's not fair!" is as strong as saying "wait, but this is a singles tournament, that ICs player gets to use 2 characters, that's not fair!" We could give you a level 3 cpu teammate if we really wanted to make things superficially "fair", but that would be stupid since it's missing the point of the ICs character design, just like 1111 misses the point of Mii character design.
#2: "It's a logistical nightmare to set up your character on every setup."
This argument is actually a good one. Speaking as a TO who runs smash 64 tournaments with finicky custom controller adapters, I sympathize with this completely. However, when we made the decision to ban wireless controllers for example, it wasn't based out of gut instinct, unlike mii fighters. We had multiple occurrences of interference with tournament sets to be able to say "okay, this is slowing us down, stick with wired controllers". Once again, no such treatment for mii setup. Furthermore I would like to see if mii setup is any worse than the standard 2 minutes searching for a name -> oh my name's not on here -> time to go make one -> **** I accidentally went back to the title screen -> uh oh the list is full -> hmm who do I delete -> okay what name should I make -> oh crap I forgot to set X to grab.... that we've been experiencing since Brawl and is perfectly allowed. Logistics is a good argument but it needs sufficient data first, which it doesn't have.
#3: "I don't want to learn how to fight 81 combinations of specials."
This is probably the most intellectually honest argument there is against mii specials, but nobody will admit to this reasoning because they don't want to sound lazy. It's fine dudes, this is the most consistent argument you can make against mii specials. Has NA by and large stuck with the vanilla meta because we don't want to learn 81 * 50 something setups, or is it because we mostly don't think the customs meta is balanced based on what seems like substandard testing on behalf of the developers and minimal attention in update patches? If it's the former, then yes, go ahead and keep the 1111 restriction (see argument #5) or ban miis altogether. If it's the latter, keep their specials, because as John#s demonstrated, that happenstance doesn't apply to them and they're being balanced for use in a vanilla meta.
#4: "Developer intent is irrelevant."
Ahh yes, the mantra of every Smash 4 player who tried out Melee once and learned what wavedashing was. Or better yet, the precursor to "if we cared about developer intent we'd be playing with items". First of all, item switch hasn't been a hidden feature since Smash 64. The developer intent has always been to give us a customizable sandbox fighter, which we've gotten in every iteration. The developers might like items better and like Smash as a party game, but that hasn't stopped them from giving us options. That's why we can turn items off and don't have to say to each other "okay guys, remember, you're not allowed to pick up items". The latter is an example of a surgical rule, you know, those complicated things we only add to the meta when something proves to be an issue not solvable by the game settings.
Furthermore, the vanilla meta has received more fine-tuning and balance patches from the developers, and is also the more popular metagame. I'm sure it's just a coincidence and intent really is irrrelevant.
#5: "1111 is composed of the first options for their creation in the UI, so they should be treated as defaults."
Oh wait, I'm sorry, whatever happened to "developer intent is irrelevant"? This is a good argument for a default moveset IF we can demonstrate that mii specials ought to be banned, but on its own is a weak pro-ban argument. The game's UI is not a stronger argument than its settings functionality or its metagame balance.
At the end of the day a lot of this comes down to preference and "I don't want to learn the full matchup" vs "I don't mind learning the full matchup". That's why it would have made more sense all along to let the game decide what's legal first under the settings in the "Rules" menu that we provide, and ban it later if it proves to be a problem. That's a method backed up by Smash's entire history. If there is a case to ban mii specials, then the way it should have happened would be for opponents to provide the data for it or make compelling arguments for it. Instead the status quo has been to ban something we had no business banning in the first place, and none of the evidence supporting their legality is enough to overcome the emotional arguments from opponents.
Full disclosure: I'm a Jigglypuff main. I do not play Mii in any capacity, or even enjoy fighting vs their specials, but I can't in good conscience side myself with the anti-specials side when their arguments seem very poor to me.
Addendum: These are not arguments in favour of lifting the ban. They're reasons why pro-ban arguments are bad. For as much as the pro-ban side likes to tout "consistency", consistency would have been putting the onus on the pro-ban side in the first place.